1. Limited Copyright Waiver
A portion of the disclosure of this patent document contains computer code listings to which the claim of copyright protection is made. The copyright owner has no objection to the facsimile reproduction by any person of the patent document or the patent disclosure, as it appears in the U.S. Patent and Trademark Office patent file or records, but reserves all other rights whatsoever.
2. Field of the Invention
The present invention relates generally to data storage systems, and more particularly to network file servers. The present invention specifically relates to a network file server distributing remote copy data over a network using the Internet Protocol (IP).
3. Description of the Related Art
Remote copy systems have been used for automatically providing data backup at a remote site in order to insure continued data availability after a disaster at a primary site. Such a remote copy facility is described in Ofek, U.S. Pat. No. 5,901,327 issued May 4, 1999, entitled “Bundling of Write Data from Channel Commands in a Command Chain for Transmission over a Data Link Between Data Storage Systems For Remote Data Mirroring,” incorporated herein by reference. This remote copy facility uses a dedicated network link and a link-layer protocol for 1:1 replication between a primary storage system and a secondary storage system.
More recently there has arisen a need for wide-area distribution of read-only data. This need typically arises when wide-area distribution of the read-only data would prevent remote users from overloading a local server, and would reduce signal transmission delay because the remote users could access remote copies nearer to them. The wide-area distribution of the read-only data is complicated by the need for consistent updates to the remote copies. It is desired for these updates to be made automatically over the wide-area network, and concurrently with read-only access to the remote copies.